Starting tubes through a drawing die

ABSTRACT

A pre-formed point member is welded onto the leading end of a pipe prior to cold drawing of the pipe and recovered for reuse after the drawing operation. This point member is capable of being cold drawn through numerous reducing dies without being replaced.

United States Patent 1191 Katunich et al. 5] Nov. 4, 1975 [54] STARTING TUBES THROUGH A DRAWING 457,222 8/1891 Serve 72/283 DIE 718,671 1/1903 Stiefel et al 72/283 1,031,000 7/1912 Higgin 29/190 Inventors: Samuel Kawnlch, Baldwm g 1,913,206 6/1933 Littler 72/370 George C. McKelvey, PO11 V116 3,415,099 12/1968 Biginelli 72/370 Borough, both of Pa. 3,570,297 3/1971 Matthews 72/283 [73] Assignee: United States Steel Corporation, FOREIGN PATENTS OR APPLICATIONS Pittsburgh, 798,481 7/1958 United Kingdom 72/284 765,799 l/l957 United Kingdom.... 72/283 [22] 1973 458,737 12/1936 United Kingdom.... 72/283 [21] Appl. No.: 343,077 5 5,268 4/1887 United Kingdom 72/283 Relted Application Dam Primary Examiner-C. W. Lanham [63] Continuation of Ser. No. 53,602, July 9, 1970, Assistant E i M J Keenan abandoned Attorney, Agent, or Firm-William A. Danchuk [52] US. Cl. 72/274 [51 rm. c1. 8210 5/00; 1321c 1/16 [57] ABSTRACT [58] Field of Search 72/283, 284, 274, 370, A tire-formed Point member is Welded Onto the lead- 72/367; 29/19() 2 2 DIG. 15 ing end of a pipe prior to cold drawing of the pipe and recovered for reuse after the drawing operation. This {56] References Ci d point member is capable of being cold drawn through UNITED STATES PATENTS numerous reducing dies without being replaced.

231,852 8/1880 Ritchie 72/283 7 6 Drawing Figures US. Patent Nov. 4, 1975 3,916,664

' FIGZZ. F7615.

STARTING TUBES THROUGH A DRAWING DIE This is a continuation of application Ser. No. 53,602, filed July 9, 1970, now abandoned.

The present invention relates generally to cold drawing processes, and, more particularly, to an improved method of pointing tubes prior to drawing, and to a weldable point member for introducing tubes to drawing dies.

Conventional practice in the cold drawing of tubes requires that one end of each tube be pointed." That is, a portion of one end of the tube is sufficiently reduced in diameter to enter the opening in a drawing die, and for a sufficient length to protrude through the die and far enough beyond to enable the tube end to be firmly gripped in the jaws of a plier or gripping mechanism. After the drawing operation, the pointed portion of the tube is cut off and scrapped. Examples of tube drawing machines are disclosed by U.S. Pat. Nos. 718,671 and 1,951,073.

Pointing is conventionally accomplished by hot forging or hot rotary swaging. In either case the tube end must be heated to forging temperature prior to hot working. Differential strains result from hot working or from cooling from the forging temperature, and are accompanied by residual stresses. Thus certain grades of steel require a stress-relieving heat treatment prior to cold drawing.

Conventional pointing operations often result in axial misalignment of the tube body and the point, and lack of symmetry of the point. These problems, and a differential between the cohesive strength of the tube body and pointed portion, and other characteristics, such as grain size, tend to cause the point to break during the drawing process. Where the tube is to be reduced in two drawing passes, the tube is usually pointed a single time. However, where the tube is to be drawn through more than two passes, it is generally re-pointed after each draw. The conventional pointing process lends itself to neither automation nor in-line processing. In the cold drawing of thin-walled tubes, especially those over three inches in diameter, the point often collapses.

It is the primary object of our invention to provide an improved method of pointing the end portion of a tube so that it can be drawn through a die.

It is another object to provide a point member for introducing a tube to a drawing die, which member is in accurate axial alignment with the tube body and is symmetrical.

It is a further object to provide a point member that will not collapse.

It is another object to provide a point member that enables a tube to be drawn through many passes without re-pointing.

It is another object to provide a strong tube point member that is capable of being attached to a tube during an in-line step of the drawing process, which step is capable of being automated.

It is a further object to provide a method of pointing tubes to be cold drawn without necessitating a heat treating step prior to cold drawing.

Our invention comprises a pre-formed or machined point member which is fixedly attached to a tubular product to be cold drawn by means such as friction welding. The invented method comprises the steps of pre-forming or machining a point member, attaching it to the end ofthe tube, and introducing it to the drawing apparatus.

FIG. I is a side view, partly in section, of a tube pointed in accordance with this invention being cold drawn.

FIG. 2 is a longitudinal-sectional view on a larger scale of a tubular pre-formed point attached to a tube.

FIG. 3 is a longitudinal-sectional view of an alternative embodiment in which the pre-formed point has a solid portion.

FIG. 4 is a longitudinal-sectional view of another alternative embodiment.

FIG. 5 is a longitudinal-sectional view of another alternative embodiment in which the point is partly conical.

FIG. 6 is a side view of yet another alternative embodiment in which the point has steps of increasing diameter.

Referring now to the drawings, reduction of tube 10 is accomplished by pulling it through die 12. The diameter of one end portion of point member 14 has been reduced to enable a gripping mechanism, not shown, to grasp the point. A mandrel 15 supports the inside surface and controls the internal diameter of the tube as it is drawn.

In accordance with our invention, tube (FIG. 2) may be beveled at end 22. A point member 23 is preformed by some suitable forming method such as forging or swaging. Point member 23 comprises a smaller diameter cylindrical portion 24 and a coaxial larger diameter cylindrical portion 25 connected by a symmetrical segment 26 of any suitable geometric shape. The point member is fixedly attached to tube 20 by friction welding.

Machined point member 30 (FIG. 3) comprises a solid cylinder 31, an optional gripping knob 32 and a cylindrical end portion 33. The point member is friction-welded to tube end 34. The knob 32 provides a positive mechanical seat for the gripper jaws. Cylinder 31, being solid, is not subject to being crushed.

Point member (FIG. 4) is similar to the point member 23, but includes a flared end 42 to give the gripper jaws a positive seat.

Point member (FIG. 5) comprises a cone 52, cylindrical shank 53, and gripping ridges 55. After reduction of each tube is completed, this point and point member (FIG. 6) can be used as points of smaller tubes until they can no longer enter a die, or until the work-hardening from so many reductions causes them to become so brittle that they break.

Point member 60 comprises a series of coaxial cylinders starting with shank 62, and each succeeding cylinder from the shank has a greater diameter. A radius 63 or bevel 64 may be machined on the corner of each cylinder for ease in entering a drawing die.

It is readily apparent that alternative point configurations are limitless. However, each point would be characterized by the following:

The point member can be fabricated from an alloy steel of any desired strength. Thus a high strength alloy would reduce the possibility of a point member breaking during the drawing operation. Conversely, a low strength alloy would provide a safety valve, in that the point member would break rather than the more expensive drawing equipment.

Since the tube to be drawn has not been heated t forging temperature, no heat treatment is required prior to cold drawing.

The point member has an easily reproducibe symmetry because its production can be subject to quality control.

Attachment of the point member is a readily automated procedure, and can be done in line.

The point member may be cut from the tube and reused after cold drawing is completed. If the final diameter of the tube is reduced by cold working, the point member can subsequently be used to draw a pipe with a smaller diameter.

From the foregoing, it is readily apparent that we have provided an improved method of pointing a tube end for cold drawing, which method precludes the necessity for heat treating prior to drawing, and is readily adaptable to automated operation. We have also provided a point member that is geometrically uniform, and in axial alignment with the tube to be drawn. The point member can also be drawn through many dies before it must be discarded.

We claim:

1. Apparatus for cold drawing a steel tube comprising:

a drawing die,

a steel tube to be cold drawn through said die, said tube having a substantially circular cross-section and an external diameter greater than the internal diameter of said die;

a mandrel for internally supporting said tube and controlling the internal diameter thereof;

a reusable steel point member removably attached to the exterior of said steel tube, said steel point member being configured to obviate the need for forging said steel tube when the two are attached, said point member having a circular cross-section concentric with its longitudinal axis, one end of said point member removably attached to said steel tube having a large diameter, the other end having a substantially smaller diameter, the external diameter of said member increasing incrementally from one end to the other, the external diameter of the larger end being greater than the internal diameter of said tube to be drawn and having as its upper limit the external diameter of said tube, the external diameter of the smaller end being less than the internal diameter of said die, the larger end of said point member being substantially hollow, the smaller end having a cylindrical shank to provide a gripping surface for a gripping mechanism whereby said point member can be removed from said tube and reused in a subsequent operation. 2. Apparatus as defined in claim 1, furthercomprising an integral gripping means on said shank, the external diameter of said means being less than the internal diameter of said die.

3. Apparatus as defined in claim 2 in which said gripping means is a knob.

4. Apparatus as defined in claim 2 in which said gripping means is a plurality of rings.

5. Apparatus as defined in claim 1, in which said point member is tubular.

6. Apparatus as defined in claim 5 further comprising a gripping means on the smaller end.

7. Apparatus as defined in claim 6 in which said gripping means is a flare on the smaller end of said point member.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 23161664 4 Mmhn'r A 197';

Inventor(s) Samuel Katunich et a1.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Signed and Scaled this [SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN second D3) Of March 1976 Atlesii'lg ff v Commissioner ufPaIents and Trademarks 

1. Apparatus for cold drawing a steel tube comprising: a drawing die, a steel tube to be cold drawn through said die, said tube having a substantially circular cross-section and an external diameter greater than the internal diameter of said die; a mandrel for internally supporting said tube and controlling the internal diameter thereof; a reusable steel point member removably attached to the exterior of said steel tube, said steel point member being configured to obviate the need for forging said steel tube when the two are attached, said point member having a circular cross-section concentric with its longitudinal axis, one end of said point member removably attached to said steel tube having a large diameter, the other end having a substantially smaller diameter, the external diameter of said member increasing incrementally from one end to the other, the external diameter of the larger end being greater than the internal diameter of said tube to be drawn and having as its upper limit the external diameter of said tube, the external diameter of the smaller end being less than the internal diameter of said die, the larger end of said point member being substantially hollow, the smaller end having a cylindrical shank to provide a gripping surface for a gripping mechanism whereby said point member can be removed from said tube and reused in a subsequent operation.
 2. Apparatus as defined in claim 1, further comprising an integral gripping means on said shank, the external diameter of said means being less than the internal diameter of said die.
 3. Apparatus as defined in claim 2 in which said gripping means is a knob.
 4. Apparatus as defined in claim 2 in which said gripping means is a plurality of rings.
 5. Apparatus as defined in claim 1, in which said point member is tubular.
 6. Apparatus as defined in claim 5 further comprising a gripping means on the smaller end.
 7. Apparatus as defined in claim 6 in which said gripping means is a flare on the smaller end of said point member. 